Trains move millions of travellers each year and have significant advantages over other forms of transportation. One disadvantage of train travel, however, is the danger posed by the abrupt edge of train platforms. Train platforms must end abruptly to allow access to the train doors by travellers. However, before the train comes to a complete stop in the station, this abrupt edge poses a hazard to passengers who do not carefully watch where they are going. There have been instances where a person has unintentionally walked off of the end of a platform and been injured. The danger of stepping off the edge of the platform is particularly acute for visually impaired persons.
Solutions to this problem have been less than fully satisfactory. For example, some platforms have lights at the edge which blink when a train approaches. The subway (or "Metro") system in Washington, D.C. has such a system. However, before a train approaches the lights do not blink and, even when the lights are blinking, a visually impaired passenger, or a passenger who is not looking in the area of the track edge, may not see the lights.
Another solution was proposed in U.S. Pat. No. 937,375, which issued in 1909. This solution features a ramp extending from a cavity near the edge of the platform and into the track area where the trains run. The ramp is connected to a "buffer-plate" that extends into the track area in a position such that a train-entering the station will strike the buffer-plate and push it towards the platform. The motion of the buffer plate causes the ramp to swivel down and become level with the platform, reducing the gap between the edge of the platform and the train. Although the ramp may serve as a warning to passengers that they are approaching the platform edge before the train enters the station, the movement of the ramp as the train contacts the bufferplate can be potentially hazardous. A passenger on the ramp may fall when the ramp moves or may walk off of the edge of the ramp before the train comes to a full stop.